The conventional manner for manufacturing various series of plug-in bulbs is that a bulb must be mounted on and soldered to a screwed brass head after the bulb has been shaped. This process is very complicated such that a defect in contact due to the poor treatment applied to the lead-in-wires will easily be induced when the bulb is being mounted and soldered to the brass head and thereby shorten the life of the light bulb. Furthermore, when the brass head is inserted onto the bulb base, the brass head more or less exposes to the bulb base. This may easily cause a dangerous accident. However, the brass head has been widely used in practice even though it is very uneconomical. On the other hand, the various conventional series of plug-in light bulbs are unable to be manufactured by means of a continuous process, leading to the waste both in labor and materials. This fact has been recognized as non-progressive in the environment of today's efficiency-oriented era. Moreover, as various conventional series of screwed light bulbs must be mounted and dismounted by means of the screw driving method, they are not convenient to be handled. Furthermore, when the screw pitch between the brass head and the bulb base is large, the light bulb will tilt if it is not positioned properly. This will be the cause of incomplete contact and certainly is not user-friendly.
A wedge type light bulb is manufactured by an integrated shaping process, and employed for electrical appliances draining a small electrical current. It not only demands high cost but also restricts itself from being widely adopted for various kinds of electrical appliances. Therefore, it can not be utilized economically and practically.
It is well known that the Wedge light bulbs are used with electrical appliances which drain a small current. Thereby the tungsten filament used by the Wedge light bulb should not be very long, such that its external shape appears as a peanut. However, if the aforesaid light bulb is used for large current electrical appliances, its tungsten filament must be lengthened to allow a large current to flow through it. Because the opening of the neck of the Wedge light bulb is so narrow that, the tungsten filament will not be easily inserted into the bulb through the opening.